Miniaturized waveguide filter based on equivalent surface plasmon polaritons

Abstract

The invention discloses a miniaturized waveguide filter based on equivalent surface plasmon polaritons. The miniaturized waveguide filter comprises a bottom-layer metal waveguide, a top-layer metal cavity connected with the upper surface of the bottom-layer metal waveguide and a metal grid piece arranged between the bottom-layer metal waveguide and the top-layer metal cavity. The two sides of the bottom layer metal waveguide are communicated, the opening face of the top layer metal cavity faces downwards and is communicated with the upper surface of the bottom layer metal waveguide, and the metal grid piece is provided with a plurality of grid units at equal intervals. The broadband, low-insertion-loss and miniaturized waveguide filter based on the equivalent surface plasmon polaritons is achieved, the design is simple, the design time is shortened, and the design efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of microwave components, and in particular to a miniaturized waveguide filter based on equivalent surface plasmons. Background Art

[0002] Metal waveguide filters are widely used in microwave or millimeter wave relay communications, microwave measurement, radar and other systems due to their high power capacity, low insertion loss, high mechanical strength and other advantages. They are important passive devices for suppressing interference signals. However, due to the inherent large size and weight of traditional waveguide filters, it is difficult to meet the miniaturization requirements of advanced communication systems.

[0003] At present, the technologies for miniaturizing waveguide filters are: first, designing filters based on substrate integrated waveguide technology, but the power capacity is much lower than that of metal waveguide filters; second, using light metal materials or synthetic materials, but the reliability is low and it is difficult to use in harsh environments; third, using theoretical methods that are different from traditional theories to design filters, but such methods are often difficult to design filters and have long simulation cycles. In addition, metal waveguide filters are often used to design narrowband filters, and it is not easy to realize broadband filters.

[0004] Equivalent surface plasmons can effectively improve the performance of traditional devices, showing great potential in improving traditional microwave system devices. However, the existing filter design based on equivalent surface plasmons mainly relies on substrate integrated waveguide technology, which is difficult to meet the needs of high power capacity and miniaturization. Therefore, how to achieve broadband, low insertion loss, and miniaturized waveguide filters is still a major challenge in filter design. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention proposes a miniaturized waveguide filter based on equivalent surface plasmons, aiming to achieve wide bandwidth, low insertion loss and miniaturization of the waveguide filter.

[0006] The present invention is implemented by the following technical solutions: A miniaturized waveguide filter based on equivalent surface plasmon polaritons, characterized in that it comprises a bottom metal waveguide, a top metal cavity connected to the upper surface of the bottom metal waveguide, and a metal grid sheet arranged between the bottom metal waveguide and the top metal cavity;

[0007] The bottom metal waveguide and the top metal cavity are placed up and down, and the inner top surface of the top metal cavity is parallel to the inner bottom surface of the bottom metal waveguide; the two sides of the bottom metal waveguide are connected, and the opening surface of the top metal cavity faces downward and is connected to the upper surface of the bottom metal waveguide; the metal grid sheet is arranged at the intersection of the opening surface of the bottom metal waveguide and the top metal cavity, and the metal grid sheet has a plurality of grid units with equal spacing.

[0008] Furthermore, the low-frequency cutoff frequency of the passband is controlled by adjusting the width W1 of the bottom metal waveguide, and the high-frequency cutoff frequency of the passband is controlled by adjusting the width W2 of the top metal cavity opening.

[0009] Furthermore, the cavity structure of the top metal cavity is a trapezoidal structure, and the bottom metal waveguide is a rectangular waveguide.

[0010] Furthermore, a rectangular parallelepiped groove for placing the metal grid piece is provided above the bottom metal waveguide.

[0011] Furthermore, each metal grid unit, the top metal cavity, and the bottom metal waveguide form an equivalent surface plasmon unit.

[0012] Furthermore, the overall size of the miniaturized waveguide filter is 1.3λ0×1.27λ0×1.3λ0, wherein λ0 is the wavelength corresponding to the operating frequency of the filter.

[0013] Furthermore, the internal mode of the miniaturized waveguide filter is a hybrid mode when it is working, specifically including an equivalent surface plasmon surface wave mode and a TE 10 model.

[0014] Furthermore, the overall structure of the miniaturized waveguide filter is symmetrical about the axis.

[0015] Furthermore, the out-of-band high-frequency suppression frequency of the filter is controlled by adjusting the upper side length of the trapezoidal cavity.

[0016] Compared with the prior art, the present invention has the following advantages and positive effects: (1) Broadband: The present invention controls the low-frequency cutoff frequency of the passband by adjusting the lateral width W1 of the bottom metal waveguide and controls the high-frequency cutoff frequency of the passband by adjusting the lateral width W2 of the top metal cavity, thereby achieving adjustable passband and realizing the broadband design that is difficult to achieve with traditional metal waveguide filters. (2) Low insertion loss: The propagation mode of the miniaturized waveguide filter based on equivalent surface plasmon is a hybrid mode, including the surface wave mode of equivalent surface plasmon and TE 10 mode, compared with a single mode, the surface wave mode has a stronger binding ability, so the transmission performance is excellent. (3) Miniaturization. The size of the miniaturized waveguide filter based on equivalent surface plasmon proposed in the present invention is only 1.3λ0×1.27λ0×1.3λ0, where λ0 is the wavelength at the corresponding operating frequency. Compared with the traditional filter, the size is greatly reduced, the length of the waveguide transition section is reduced, and the structure is more compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention.

[0018] Figure 2 It is a side sectional view of the overall structure of an embodiment of the present invention.

[0019] Figure 3 It is a schematic diagram of the structure of the top metal cavity, bottom metal waveguide and metal grid sheet of the present invention.

[0020] Figure 4 It is a schematic structural diagram of an equivalent surface plasmon unit of the present invention.

[0021] Figure 5 It is a dispersion curve diagram of the equivalent surface plasmon unit of the present invention.

[0022] Figure 6 Graph 1 is the transmission coefficient of the embodiment of the present invention when the bottom metal waveguide has different widths W1.

[0023] Figure 7 Graph 1 is the transmission coefficient of the embodiment of the present invention when the width W2 of the top metal cavity is different.

[0024] Figure 8 2 is an S parameter diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to clearly illustrate the technical features of this patent, this patent is elaborated in detail below through a specific implementation method and in combination with its accompanying drawings.

[0026] like Figures 1 to 4 As shown, an embodiment of a miniaturized waveguide filter based on equivalent surface plasmon polaritons is shown, which includes: a bottom metal waveguide 1, a top metal cavity 2, a metal grid plate 3 and two flanges 4, which are standard WR-90 flanges.

[0027] The bottom metal waveguide 1 and the top metal cavity 2 are placed up and down, and the inner top surface of the top metal cavity 2 is parallel to the inner bottom surface of the bottom metal waveguide 1; the two sides of the bottom metal waveguide 1 are connected, and the opening surface of the top metal cavity 2 faces downward and is connected to the upper surface of the bottom metal waveguide 1; the metal grid sheet 3 is arranged at the intersection of the opening surface of the bottom metal waveguide 1 and the top metal cavity 2, and the metal grid sheet 3 has a plurality of grid units with equal spacing, and the three are fixed into a whole through the metal through holes on both sides, and the two flanges 4 are respectively connected to the two sides of the above-mentioned whole.

[0028] In this embodiment, the width W1 of the bottom metal waveguide controls the low-frequency cutoff frequency of the filter passband, the width W2 of the top metal cavity is the same as the width of the metal grid plate, and the width W2 of the top metal waveguide controls the high-frequency cutoff frequency of the filter passband.

[0029] In this embodiment, the cavity structure of the top metal cavity is a trapezoidal structure cavity, the upper side length of the trapezoidal structure is 0.5 mm, the lower side length is 12.1 mm, and the height is 10.16 mm. The out-of-band high-frequency suppression frequency of the filter is controlled by adjusting the upper side length of the trapezoidal cavity.

[0030] Please combine Figure 3 , the figure shows a schematic diagram of the structure of the top metal cavity, bottom metal waveguide, and metal grid sheet of the present invention. The cavity structure of the top metal cavity is a trapezoid. In this embodiment, the cross-sectional dimensions of the bottom metal waveguide are standard WR-90 waveguide cross-sectional dimensions. The metal grid sheet includes 30 equally spaced grid units, each grid unit has a length P of 1 mm and a thickness of 0.2 mm. There is a 31.6×30.86×0.6 mm rectangular groove above the bottom metal waveguide for placing the metal grid sheet. Combined with Figure 4 , the figure shows the equivalent surface plasmon unit structure of the present invention, and its unit period is equal to the grid unit length, which is 1 mm.

[0031] like Figure 5 The figure shows the eigenmode dispersion curve of the equivalent surface plasmon unit structure. The starting frequency point of the curve is the low-frequency cutoff frequency of the corresponding filter passband, and the asymptotic frequency point is the high-frequency cutoff frequency of the corresponding filter passband.

[0032] Figure 6 is the transmission coefficient of this embodiment when the bottom metal cavity has different widths W1. The wider the bottom metal waveguide width W1 is, the lower the starting frequency of the equivalent surface plasmon unit dispersion curve is, and the lower the low-frequency cutoff frequency of the corresponding filter is.

[0033] Figure 7 is the transmission coefficient of this embodiment when the width W2 of the top metal cavity is different. The wider the width W2 of the top metal cavity is, the lower the asymptotic frequency of the equivalent surface plasmon unit dispersion curve is, and the lower the high-frequency cutoff frequency of the corresponding filter is.

[0034] Figure 8 The S parameters of the 6.6-12 GHz bandpass filter finally designed for this embodiment are shown in the figure. In the range of 6.6-12 GHz, the filter of this embodiment has good passband characteristics, the return loss is greater than -15 dB, and the insertion loss at the center frequency of 9.3 GHz is about 0.05 dB. In addition, the filter has a certain out-of-band suppression performance, and its attenuation is greater than -40 dB. At about 14.5 GHz, the stopband performance begins to decline because higher-order modes will be transmitted in the equivalent surface plasmon waveguide.

[0035] In summary, the miniaturized waveguide filter based on equivalent surface plasmon provided by the present invention controls the low-frequency cutoff frequency of the filter passband by adjusting the width W1 of the bottom metal waveguide, and controls the high-frequency cutoff frequency of the filter passband by adjusting the width W2 of the top metal cavity. The passband of the miniaturized waveguide filter based on equivalent surface plasmon is finally designed to be 6.6 GHz-12 GHz. The filter of the present invention has the advantages of wide bandwidth, low insertion loss and miniaturization.

[0036] In addition, there are many specific implementation methods of the present invention, and the above is only a preferred implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, if it does not deviate from the principle of the present invention, it is also possible to make such improvements and modifications, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A miniaturized waveguide filter based on equivalent surface plasmon, characterized in that: The invention comprises a bottom metal waveguide, a top metal cavity connected to the upper surface of the bottom metal waveguide, and a metal grid sheet arranged between the bottom metal waveguide and the top metal cavity; the bottom metal waveguide and the top metal cavity are placed up and down, and the inner top surface of the top metal cavity is parallel to the inner bottom surface of the bottom metal waveguide; the two sides of the bottom metal waveguide are connected, and the opening surface of the top metal cavity faces downward and is connected to the upper surface of the bottom metal waveguide; the metal grid sheet is arranged at the intersection of the opening surface of the bottom metal waveguide and the top metal cavity, and the metal grid sheet has a plurality of grid units with equal spacing.

2. The miniaturized waveguide filter based on equivalent surface plasmon according to claim 1, characterized in that: The low-frequency cutoff frequency of the passband is controlled by adjusting the width W1 of the bottom metal waveguide, and the high-frequency cutoff frequency of the passband is controlled by adjusting the width W2 of the top metal cavity opening.

3. The miniaturized waveguide filter based on equivalent surface plasmon according to claim 1, characterized in that: The cavity structure of the top metal cavity is a trapezoidal structure, the bottom metal waveguide is a rectangular waveguide, and a rectangular parallelepiped groove for placing a metal grid piece is provided above the bottom metal waveguide; each metal grid unit, the top metal cavity and the bottom metal waveguide form a sub-wavelength periodic unit.

4. The miniaturized waveguide filter based on equivalent surface plasmon according to claim 1, characterized in that: The overall size of the miniaturized waveguide filter is 1.3λ0×1.27λ0×1.3λ0, where λ0 is the wavelength corresponding to the operating frequency of the filter.

5. The miniaturized waveguide filter based on equivalent surface plasmon according to claim 1, characterized in that: The overall structure of the miniaturized waveguide filter is symmetrical about an axis.

6. The miniaturized waveguide filter based on equivalent surface plasmon according to claim 1, characterized in that: The out-of-band high frequency suppression frequency of the filter is controlled by adjusting the upper side length of the trapezoidal cavity.

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